Hydraulic system

ABSTRACT

The invention relates to an improvement in the hydraulic system of the type having a control unit for controlling the operating functions of the system, and wherein the control unit includes a housing having an internal passage through which the hydraulic fluid must flow, and a plurality of function-controlling components in the housing and acting upon the fluid flow and whose operation can be deleteriously influenced by contaminants in the hydraulic fluid. The improvement provides for a fluid filter to be accommodated directly in the housing of the control unit, being interposed in the passage upstream of the functioncontrolling components, so as to remove contaminants from the hydraulic fluid just prior to passage of the fluid to the function-controlling components.

[ Sept. 23, 1975 Aspinwall et a1.

[ HYDRAULIC SYSTEM Courson.................,............. 210/130 Inventor: Otmar Schiin, Scheidterberg,

Germany Primary ExaminerHenry T. Klinksiek A .1 h c a b h Gm un arm ddf

yye

[22] Filed: 1974 The invention relates to an improvement in the hy Appl. No.: 463,779

draulic system of the type having a control unit for controlling the operating functions of the system, and

wherein the control unit includes a housin internal passage through which the h must flow, and a plurality of function ponents in the housing and acting u and whose operation can be delete g having an by contaminants in the hydraulic fluid. The im ment provides for a fluid filter to be accomm 2 002 1 303 3 l l n ma 3 1. O 2 ZDB H .9 a 4 0 t 4B1 a 5 2 0 7 m9 w m .4 n .mfi .m r. m" n y m m .m m I t n a m H .m a m m 1 1 G u D. mmw A3 mm "we .W mus e a .2 mm mm F d m Std A u IF .1 1]] 0 218 3 555 .1 [1:1

directly in the housing of the control unit, being interposed in the passage upstream of the functioncontrolling components, so as to remove contaminants from the hydraulic fluid just fluid to the function prior to passage of the -controlling components.

3,072,260 Szwargulski et a]. 210/130 X 3,312,353 3,476,251 3,545,616

i2 4 Claims, 4 Drawing Figures Rosaen 11/1969 Kud1aty........................... 12/1970 Aspinwall et a1.

F I l::::: 111------ Fig. 1

US Patent Sept. 23,1975 Sheet 2 of4 3,906,994

F. f i i i 7 a 0-- 0.]; A? QIL I m I 0* A Flg 2 US Patent Sept. 23,1975 Sheet30f4 3,906,994 v Fig.3

US Patent Sept. 23,1975 Sheet4 (4 3,906,994

HYDRAULIC SYSTEM BACKGROUND OF THE INVENTION The present invention relates to thefield of hydrau lies in general, and more particularly to a hydraulic system. Still more specifically, the invention relates to a hydraulic system of the type having a control unit for controlling the operating functions of the system.

Generally speaking, a hydraulic system requires a reservoir for hydraulic fluid, a pump for pumping the hydraulic fluid through conduits, a hydraulie-fluid user, and various funetion'controlling components such as valves or the like, which control the function of the system, It is known in the prior art to provide such systems with control units which accommodate the functioncontrolling components in a housing, and to combine the housing with the pump and the fluid reservoir to form an assembly. Such an assembly is known in the art as a hydro aggregate and represents a substantial simplification in the construction of hydraulic systems, because it is then merely necessary to connect this aggregate with the user or users via appropriate conduits. Most hydraulic systems are provided with filters which are intended to remove contaminants from the hydraulic fluid, since such contaminants can disadvantageously influence the operation of the system, especially of the function-controlling components such as valves and the like. As a general rule, the prior art mounts these filters either on the cover of the hydraulic-fluid reservoir, in which case the filter has a separate housing that can be connected to the cover, or the filter is directly interposed in the conduit which connects the control unit of the system with its fluid supply. In either case, the filter will be remote from the control unit and its associated function-controlling components, and this has the disadvantage that between the filter and the control unit additional contaminants may in some manner appear in the hydraulic fluid and replace those which have previously been filtered out ofit, so that the function-controlling components are not as effectively protected as is desirable. To be really effective the filter should be located in the immediate vicinity of the function-controlling components," but the prior art has found no way in which this can be done in a manner which is both convenient and feasible from an economic viewpoint and fromthc point of view of space requirements. Y

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to overcome the aforementioned disadvantages in hydraulic systems of the type under discussion.

More particularly, it is an object of the present invention to provide, in a hydraulic system of-the type having a control unit provided with a housing and function: controllingcomponents in the housing, a way. in which a filter for filtering contaminants. from the hydraulic fluid of the system can be accommodated directly in the housing in the immediate vicinity of the functioncontrolling components which are primarily to be protected against interference from such contaminants.

Another object of the invention is to provide such an arrangement wherein this inclusion of the filter can be carried out. entirely independently of any other considerations relating to the ,overall structure of the system or the space availability.

In keeping with the above objects, and others which will become apparent hereafter, one feature of the invention resides, in a hydraulic system of the type having a control unit for controlling the operating functions of 5 the system, and wherein the control unit includes a housing having an internal passage through which the hydraulic fluid must flow, and a plurality of functioncontrolling components in the housing and acting on the fluid flow and whose operation can be deleteriously influenced by contaminants in the hydraulic fluid, in'an improvement which comprises a fluid filter that is accommodated directly in the housing and interposed in the passage upstream of the function-controlling com ponents, so as to remove contaminants from the hydraulic fluid just prior to passage of the fluid to the function-controlling components.

A particularly simple embodiment of the invention provides for the chamber in the housing, in which the filter element of the filter is accommodated, to have an opening which communicates with the exterior of the housing and through which the filter element is accessible, and for this opening to be closed by a removable cover which may be provided with bores constituting part of the internal passage.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in conneetion with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top-plan view illustrating a control unit of the type with which the present invention is concerned;

FIG. 2 is a diagrammatic showing of the fluid circuits provided in the control unit of FIG. I, and of the function-controlling components therein;

FIG, 3 is a fragmentary sectional detail view, showing a detail of FIG. I on an enlarged scale; and

FIG. 4 is a view similar to FIG. 3, but illustrating a different embodiment of the invention.

I DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring firstly to the embodiment illustrated in FIGS. 1-3 it will be seen that reference numeral 1 identifies a control unit for controlling theoperating functions of a hydraulic system. The details of the system, which are entirely conventional and well known to those conversant with the field, have not been illustrated. The control unit 1 has a housing which is provided with a plurality of ports, A, B, P and T. Some of these ports are located at the side In of the unit 1, as seen in FIG. I, and cooperate with corresponding ports of a control valve which is not illustrated but which will be connected with the control unit I in the overall organization of the hydraulic system.

The unit 1 is further provided with a pressure limiting valve 2 of known construction which can be secured to it by threading the valve into an appropriately tapped bore, and with a throttle 3 which is here in form of a threaded element that can be threaded to a greater or lesser extent into the unit 1, to thereby vary the flowthrough cross section of a passage in the interior of the unit I. The valve 2 and the throttle 3 constitute function-controllingcomponents; the purpose of the valve 2 is to protect the hydraulic system against excessive pressure increases, and the purpose of the throttle 3 is to throttle the flow of the working fluid which flows to the port P that is located at the side 1a of the control unit 1.

The ports T are in communication with the reservoir (which is not shown), and internally of the unit 1 there are formed passages t which communicate the ports T with one another and in which a filter 4 is interposed, which according to the present invention is thus located in the control unit and in the immediate vicinity of the function-controlling components which must be protected. In the embodiment of FIGS. l-3 there is further provided a bypass 5 by means of which the filter 4 can be bypassed, and a one-way valve 6 is interposed in the bypass 5.

FIG. 3 shows details of the filter in the unit 1. It will be seen that, the unit 1 is formed with a chamber 7 hav ing an opening that communicates with the interior of the unit 1 and which is closed by a removable cover 8. The filter element 9 which here is of tubular configuration, is located in the chamber 7 and defines within the same an annular compartment. The hollow interior of the filter element 9 is designated with reference numeral 20. Mounted at the opposite axial ends of the filter element 9 are flanges 10 and 11, respectively, which are fluid-tightly connected with the filter element 9 and which each have a central opening.

The cover 8 is formed with a nipple 12 which embraces and retains a housing 13 of the one-way valve 6. One portion of this housing 13 extends into the interior of the nipple l2, and the other portion extends through the opening in the flange 10, so that the housing 13 is thus firmly held in place by the nipple 12 of the cover 8, and serves to also retain the filter element 9 itself against displacement. The end of the chamber 7 that is remote from the cover 8 is also formed with a nipple,

identified with reference numeral 21, which extends through the opening in the flange 11, thus firmly holding the filter element 9 in place in conjunction with the nipple 12. The opening passage of the nipple 21 is identified with reference numeral 22.

Aecommodated in the housing 13 of the valve 6, which housing is formed with two oppositely located openings 14 one of which communicates with the interior 18 of the nipple 12 and the other of which communicates with the interior 20 of the filter element 9, is a valve member 15 which is normally biased into and seals the opening of the housing 13 which communicates with the interior 18 of the nipple 12.

An inlet opening 19 communicates with the chamber 7 exteriorly of the filter element 20, so that in normal operation fluid entering through the inlet opening 19 will enter the chamber 7 and will be compelled to pass through the filter element 9 into the interior 20 thereof, from where it then flows via the outlet 22 of the nipple 21 into the passages I. If, however, the filter element 9 should be clogged with retained contaminants, then the pressure in the inlet opening 19 will of course build up because there will then be either no or only a substantially reduced flow of liquid through the filter element 9. When the pressure build up in the inlet opening 19 reaches a level sufficient to overcome the force with which the biasing spring 16 of the valve 6 presses the valve member 15 into the associated opening of the housing 13, the pressure of fluid which is communicated from the inlet opening 19 via a passage 17 to the interior 18 of the nipple 12, will shift the valve member 15 out of the opening in the housing 13, so that fluid can now pass through the openings 14 directly into the interior 20 of the filter element 9, and from there via the opening 22 of the nipple 21 into the passages t.

Of course, the fluid which passes through this bypass circuit will not have been filtered and will contain its contaminants, if any. However, there may be installations in which a perhaps brief flow of unfiltered hydraulic fluid is acceptable, and again there will be other installations in which it is so important that the clogging of the filter should not be permitted to interrupt the operation of the system that the possible troubles that can be caused by the temporary flowing of unfiltered hydraulic fluid through the system must be accepted as being the lesser problem than a shutting-down of the system due to clogging of the filter element 9.

If, however, it is essential that unfiltered hydraulic fluid be under no circumstances allowed to enter the passages I, then the embodiment of FIG. 4 may be utilized. This embodiment corresponds largely to that of FIGS. 1-3 and like elements are identified with like reference numerals as in those Figures.

In FIG. 4, however, the filter arrangement that is used does not have the bypass capacity that has been described and illustrated above with respect to FIG. 3.

In FIG. 4 the filter element 9 is mounted in the same way as before, except that here the bottom flange Il may simply be seated on the end wall bounding the chamber 7 remote from the cover 8, and will be sealed against entry or exit of fluid, there being no passage 22 as in the preceding embodimentv In FIG. 4 the hydraulic fluid enters via the inlet opening 23 into the chamber 7, and from there travels through the circumferential wall of the filter element 9 into the interior 20 thereof. From there the filtered hydraulic fluid enters the interior of the nipple 12 and travels into a bore 25 which is formed in the cover 8, and from where it leaves via the outlet 24 to enter into the passages IV The bore 25 thus in effect constitutes a part of the passages It is clear that in FIG. 4 there is no way in which the hydraulic fluid can bypass the filter element 9. If the latter is clogged, then the further passage of hydraulic fluid through the filter element 9 and into the passages I will simply be precluded until the problem has been rectified. However, this arrangement does, of course, have the advantage of not under any circumstances permitting the flow of unfiltered hydraulic fluid into the passages I.

The filter element 9 is of a construction known in the art, and it will be appreciated that in both of the described cmbodimcnts appropriate warning arrangements may be provided (also known from the art) which indicate (for instance visually or audibly) if and when the filter element 9 is clogged, so as to alert an operator to the fact that the filter element must be changed.

It should still be mentioned that the embodiment of FIG. 4 can also be further modified by providing the filter element 9 not in the location illustrated in FIG. 4, but instead interposing it in the passages k (see FIG. 2) which connect the pressure ports I within the unit 1.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above While the invention has been illustrated and de scribed as embodied in a hydraulic system, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge. readily adapt it for var ious applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

I. In a hydraulic system of the type having a control unit for controlling the operative functions of said systcm, and wherein the control unit includes a housing having an internal passage through which the hydraulic fluid must flow and a plurality of function-controlling elements in the housing and acting upon the fluid flow and whose operations can be delcteriously influenced by contaminants in the hydraulic fluid, the improvement comprising a chamber formed in said housing and having an inlet and an outlet communicating with said passage upstream of said function-controlling elements, and said housing having an opening communicating with said chamber; a fluid filter comprising a filter element in said chamber intermediate said inlet and said outlet so that hydraulic fluid is normally compelled to pass through said filter element and so that contaminants are removed from the hydraulic fluid just prior to passage of the fluid to said function-controlling elements; and a removable cover normally closing said opening.

2. In a hydraulic system as defined in claim 1, wherein said cover comprises an engaging portion which engages said filter element and maintains the same against displacement in said chamber.

3. In a hydraulic system as defined in claim 1, said filter element being hollow, forming in its interior a first compartment, and defining within said chamber a second compartment, said inlet communicating with one of said compartments and said outlet communicating with the other of said compartments; and wherein said cover is provided with a bore which communicates with said other compartment and with said passage.

4. In a hydraulic system as defined in claim 1, wherein said filter element is hollow, forming in its interior a first compartment, and defining within said chamber a second compartment, said inlet communicating with one of said compartments and said outlet communicating with the other of said compartments; a bypass connecting said inlet with said other compartment; and one-way valve means interposed in and normally closing said bypass, said valve means being operative to open said bypass only in response to clogging of said filter element and a consequential increase of 

1. In a hydraulic system of the type having a control unit for controlling the operative functions of said system, and wherein the control unit includes a housing having an internal passage through which the hydraulic fluid must flow and a plurality of function-controlling elements in the housing and acting upon the fluid flow and whose operations can be deleteriously influenced by contaminants in the hydraulic fluid, the improvement comprising a chamber formed in said housing and having an inlet and an outlet communicating with said passage upstream of said function-controlling elements, and said housing having an opening communicating with said chamber; a fluid filter comprising a filter element in said chamber intermediate said inlet and said outlet so that hydraulic fluid is normally compelled to pass through said filter element and so that contaminants are removed from the hydraulic fluid just prior to passage of the fluid to said function-controlling elements; and a removable cover normally closing said opening.
 2. In a hydraulic system as defined in claim 1, wherein said cover comprises an engaging portion which engages said filter element and maintains the same against displacement in said chamber.
 3. In a hydraulic system as defined in claim 1, said filter element being hollow, forming in its interior a first compartment, and defining within said chamber a second compartment, said inlet communicating with one of said compartments and said outlet communicating with the other of said compartments; and wherein said cover is provided with a bore which communicates with said other compartment and with said passage.
 4. In a hydraulic system as defined in claim 1, wherein said filter element is hollow, forming in its interior a first compartment, and defining within said chamber a second compartment, said inlet communicating with one of said compartments and said outlet communicating with the other of said compartments; a bypass connecting said inlet with said other compartment; and one-way valve means interposed in and normally closing said bypass, said valve means being operative to open said bypass only in response to clogging of said filter element and a consequential increase of fluid pressure at said inlet. 